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SFTP Upload Hangs after SSH2 patch

Posted: 08/28/2015 19:12:21
by John Evans (Basic support level)
Joined: 08/25/2015
Posts: 2

We have been using Eldos software since 2009 without any issues. We have been using the TElSimpleSFTPClient class structure to upload credit card processing files to Chase/Paymentech processor using user name and password authentication. The process is very trivial using the Eldos SFTP library. This has worked flawlessly for years. Last weekend their server was updated which included a security patch regarding SSH2. The exact nature of the update I was not able to find out. Their server is a Unix machine running HP- B.11.31 U ia64 2195039975. Since then however, the file uploads fail on files roughly between 25mb and 50mb. If I send files under 25mb they always transfer without a problem, larger files hang and no data is transferred. The connection eventually times out and the client receives a Error Code 10054. I have scoured the forum and have tried various suggestions regarding disabling all encryption algorithms and setting select ones, setting the PipeLineLength to 1, adjusting the DowloadBlockSize, setting KeepAlivePeriod, setting ASCIIMode to false, setting the AutoAdjustCiphers value.
In the interest of determining if it was in our code I ran the SimpleSFTPClient and SophisticatedClient sample C# programs you provide and they had the same problems. We do not see this problem using common (S)FTP client software such as FileZilla and CoreFTP. I tried an Open Source project SshNet as a comparison and it is able to upload files as large as 90Mb without a problem. I thought for sure that the problem could be resolved with setting changes but have tried many options all week and hove not been able to come up with a solution. I believe that this may be a bug in your library resulting from the security patch and hope very much that you may be able to offer a solution as soon as possible.
Posted: 08/28/2015 19:41:18
by Ken Ivanov (Team)

Hi John,

Thank you for contacting us. We are sorry that you are having an issue with our components.

Could you please specify the exact SecureBlackbox version and edition you are using (this is not clear from your message, unfortunately)?

And another question - do I understand right that the hangup happens right after the upload is about to commence, and not after the 25-50Mb piece of the file has been sent out to the server?

I would also kindly ask you to attach your 'license ticket' to your eldos.com site account. This will automatically assign the correct support level to your account and will let us 'see' your license and provide you with a faster assistance. You will find your license ticket in your SecureBlackbox registration letter (it's a short line of alphanumeric characters, e.g. 45175167111234589642).


Posted: 08/31/2015 12:23:46
by John Evans (Basic support level)
Joined: 08/25/2015
Posts: 2

Thank you Ken.

The version of SBB that we have been using is However, I downloaded and tried the trial version and the same problem exists. I Also tried the test sample C# SimpleSFTPClient project for both versions and the same hang condition occurs.

You are correct, the hang occurs before any data is transferred. The file is created at the server, (0 bytes) and then nothing happens until a timeout occurs and the Error Code 10054 is returned to the client. This results in an empty file on the server. Oddly enough if the file is small enough (under 25Mb roughly) the hang condition does not occur and the file is transferred without problem.

We purchased your library in November 2009 online. I do not see a licence ticket number on any of the invoice receipts that we have. So I do not know if we have one or not.


Posted: 08/31/2015 13:37:13
by Eugene Mayevski (Team)

The problem can come from different sources, it's not necessarily related to the destination server. For example the first idea that came to my mind was that opening of the source file took long time for whatever reason.

I am moving your message to the HelpDesk where we will address the licensing-related topics and discuss the ways to address your problem. Helpdesk is our easy-to-use individual support system that allows communicating and exchanging sample data with our support personnel privately. You will also get e-mail notifications about updates of your support request.

Sincerely yours
Eugene Mayevski
Posted: 11/25/2015 09:54:43
by Eugene Mayevski (Team)

For everyone who reads the topic - the problem was in the server. After a lengthy investigation we have found out that the server supports blocks of 16Kb only and PipelineLength of 1. We have added autodetection of this buggy server to SecureBlackbox 14.

Sincerely yours
Eugene Mayevski



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